This invention relates to the preparation of 2-methylene-1,3-propanediamide. More particularly, it relates to a process for preparing this monomer by a fluoride anion initiated .beta.-elimination reaction conducted in the presence of an inert, aprotic organic solvent.
U.S. Pat. No. 2,466,395, issued to J. B. Dickey, discloses the use of 2-methylene-1,3-propanediamide or, more commonly, methylene malonamide, as a comonomer for preparing copolymers useful in preparing films and filaments. The process for preparing this monomer, disclosed therein, is said to comprise a sulfuric acid or hydrogen peroxide hydrolysis of 2-methylenepropanedinitrile, i.e., ##STR3##
This preparative method has certain inherent disadvantages. One disadvantage is that 2-methylene-1,3-propanediamide tends to be unstable in the presence of such reagents as sulfuric acid and hydrogen peroxide, the monomer tending to undergo polymerization or other degradative reactions in the presence of such reagents. Thus, the reaction conditions suggested by U.S. Pat. No. 2,466,395 for preparing this monomer are generally unfavorable in terms of obtaining the desired product and especially in terms of obtaining a high yield of the desired product.
Another disadvantage of the process disclosed in U.S. Pat. No. 2,466,395 is that 2-methylenepropanedinitrile is highly toxic and, as such, is an undesirable intermediate.
A particularly useful process for preparing 2-methylene-1,3-propanediamide, which avoids the aforementioned problems and disadvantages, forms the subject matter of copending U.S. Patent application Ser. No. 109,811 of Howard C. Hass, et al filed Jan. 7, 1980. As disclosed therein, 2-methylene-1,3-propanediamide can be prepared by providing a solution of a 1,3-propanediamide, substituted at the 2-carbon atom with a trisubstituted silyl methyl group and an electron-accepting leaving group, in an inert, aprotic organic solvent and subjecting the compound in the solution to .beta.-elimination reaction conditions sufficient to eliminate the trisubstituted silyl group and the electron-accepting leaving group from the compound to form a double bond between the carbon atoms to which the trisubstituted silyl group and the electron-accepting leaving group were bonded. The present invention relates to an improved process for the preparation of 2-methylene-1,3-propanediamide by a fluoride anion-initiated .beta.-elimination reaction.